Transaction_louis.ipynb

transaction_id.ipynb

{
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  "metadata": {
    "colab": {
      "name": "Transaction_louis.ipynb",
      "provenance": [],
      "toc_visible": true,
      "collapsed_sections": [],
      "include_colab_link": true
    },
    "kernelspec": {
      "name": "python3",
      "display_name": "Python 3"
    },
    "language_info": {
      "name": "python"
    }
  },
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "view-in-github",
        "colab_type": "text"
      },
      "source": [
        "<a href=\"https://colab.research.google.com/gist/lourkeur/e8aa99f84ac42305ff18855dae083e2f/transaction_louis.ipynb\" target=\"_parent\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/></a>"
      ]
    },
    {
      "cell_type": "markdown",
      "source": [
        "# POPstellar: transaction id example implementation\n",
        "This is a simple, general-purpose implementation of the transaction hashing algorithm for documentation purposes. The algorithm receives a transaction in JSON representation and outputs a SHA-256 digest of it."
      ],
      "metadata": {
        "id": "Jr3iEbQ9f0Tr"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "def collect_strings(obj):\n",
        "  '''retrieve the string representation of every field in obj.\n",
        "\n",
        "  The resulting fields are ordered following the specification.\n",
        "  '''\n",
        "  if isinstance(obj, str):\n",
        "    yield obj\n",
        "  elif isinstance(obj, int):\n",
        "    # use decimal representation for integers\n",
        "    yield str(obj)\n",
        "  elif isinstance(obj, list):\n",
        "    # recurse into array elements in array order\n",
        "    for e in obj:\n",
        "      yield from collect_strings(e)\n",
        "  elif isinstance(obj, dict):\n",
        "    # recurse into JSON object fields in order of field names\n",
        "    for k, v in sorted(obj.items()):\n",
        "      yield from collect_strings(v)\n",
        "  else:\n",
        "    raise TypeError(f\"do not know how to collect strings from a {type(obj)}\")"
      ],
      "metadata": {
        "id": "ZKz-kvIf0tG0"
      },
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "import base64, hashlib\n",
        "\n",
        "def hash_len(strings):\n",
        "  '''hash a sequence of strings in accordance with the POPstellar protocol spec.\n",
        "\n",
        "  https://github.com/dedis/popstellar/blob/master/docs/protocol.md\n",
        "  '''\n",
        "  payload = ''.join(f\"{len(s)}{s}\" for s in strings)\n",
        "  return base64.urlsafe_b64encode(hashlib.sha256(payload.encode(\"utf-8\")).digest())"
      ],
      "metadata": {
        "id": "ouUhhWXYdI3R"
      },
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "def compute_transaction_id(transaction):\n",
        "  return hash_len(collect_strings(transaction))"
      ],
      "metadata": {
        "id": "qj9NGGZ700Tz"
      },
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "id": "r6zHfxAg0hBh"
      },
      "outputs": [],
      "source": [
        "import json\n",
        "\n",
        "example = json.loads(\"\"\"{\n",
        "\t    \"Version\": 1,\n",
        "\t    \"TxIn\": [{\n",
        "\t\t    \"TxOutHash\": \"47DEQpj8HBSa--TImW-5JCeuQeRkm5NMpJWZG3hSuFU=\",\n",
        "\t\t    \"TxOutIndex\": 0,\n",
        "\t\t    \"Script\": {\n",
        "\t\t\t    \"Type\": \"P2PKH\",\n",
        "\t\t\t    \"Pubkey\": \"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\",\n",
        "\t\t\t    \"Sig\": \"CAFEBABE\"\n",
        "\t\t    }\n",
        "\t    }],\n",
        "\t    \"TxOut\": [{\n",
        "\t\t    \"Value\": 32,\n",
        "\t\t    \"Script\": {\n",
        "\t\t\t    \"Type\": \"P2PKH\",\n",
        "\t\t\t    \"PubkeyHash\": \"2jmj7l5rSw0yVb-vlWAYkK-YBwk=\"\n",
        "\t\t    }\n",
        "\t    }],\n",
        "\t    \"LockTime\": 0\n",
        "}\"\"\")\n"
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "list(collect_strings(example))"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "3sDRRNUYd3lJ",
        "outputId": "2626154b-d046-4178-a7fd-0fee82fca48d"
      },
      "execution_count": null,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "['0',\n",
              " 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=',\n",
              " 'CAFEBABE',\n",
              " 'P2PKH',\n",
              " '47DEQpj8HBSa--TImW-5JCeuQeRkm5NMpJWZG3hSuFU=',\n",
              " '0',\n",
              " '2jmj7l5rSw0yVb-vlWAYkK-YBwk=',\n",
              " 'P2PKH',\n",
              " '32',\n",
              " '1']"
            ]
          },
          "metadata": {},
          "execution_count": 5
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "assert compute_transaction_id(example) == b'dBGU54vni3deHEebvJC2LcZbm0chV1GrJDGfMlJSLRc='"
      ],
      "metadata": {
        "id": "VR5nNYdpd1qD"
      },
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "MMDsrEO3eAer"
      },
      "execution_count": null,
      "outputs": []
    }
  ]
}